1. Field of the Invention
The present invention relates to rotating electrical machines equipped with a stator and a rotor capable of cooling a coil end of the stator and reducing a sliding loss, i.e. friction loss of the rotor.
2. Description of the Related Art
It is necessary to reduce a temperature of a stator in a rotating electrical machine, i.e. necessary to cool a coil end of a stator winding of a stator when the rotating electrical machine is rotating because a temperature of the stator winding of the stator rises due to an AC (alternating current) copper loss which is generated by a DC (direct current) copper loss and a leakage flux when electric power is supplied to the stator. For example, Patent document 1, Japanese patent laid open publication No. 2014-103722 discloses a technique for reducing a temperature of a stator in a rotating electrical machine.
The patent document 1 discloses the rotating electrical machine equipped with a housing, a rotor and a stator. The rotor has a rotor core and a rotor shaft. The rotor shaft of the rotor is rotatably supported by the housing. The rotor shaft has a lubricating fluid passage and a fluid exhaust outlet. Through the fluid discharge outlet the oil is discharged outside. The lubricating fluid passage is provided extending to a rotating axial direction of the rotor shaft of the rotor. Through the fluid exhaust outlet, fluid as a coolant flowing from the lubricating fluid passage is discharged to radially outside of the rotating axial direction. The rotor rotates around the rotor shaft in the housing. The stator is arranged at an outer peripheral side of the rotor in the housing. The stator has a stator core and a stator coil. The stator coil is wound on the stator core. The fluid exhaust outlet is open toward a coil end section which protrudes toward the axial direction of the core. The fluid exhaust outlet has an expanded section which is gradually expanded toward a radially outside of the fluid discharge outlet.
However, when the rotating electrical machine having the structure previously described is produced, it is necessary for the technique disclosed by the patent document 1 to use a complicated process in order to form an oil hole and an oil exhaust hole toward the coil end side. The oil enters the oil hole and flows in the lubricating fluid passage. Because the conventional technique further requires an oil supply pump, this increases a manufacturing cost. Further, because the rotating electrical machine having the structure disclosed by the patent document 1 has a relatively long distance which is measured from the oil exhaust hole to the coil end of the stator winding of the stator, the exhausted oil is scattered. This becomes difficult to exhaust the oil to a specific area with high accuracy.